100Fm257.000
Actinidef-blockRadioactive
Fermium
Element 100 on the periodic table, symbol Fm, group 3, period 7.
Fermium is a synthetic element with symbol Fm and atomic number 100. It is a member of the actinide series. It is the heaviest element that can be formed by neutron bombardment of lighter elements, and hence the last element that can be prepared in macroscopic quantities, although pure fermium metal has not yet been prepared.
Properties
- Atomic Number
- 100
- Atomic Mass
- 257.0000 u
- Group
- 3
- Period
- 7
- Block
- f-block
- Category
- Actinide
- State at 25 °C
- Solid
- Melting Point
- 1,800 K · 1,526.9 °C
- Boiling Point
- Not measured
- Density
- Not measured
- Atomic Radius
- Not measured
- Electronegativity
- 1.3
- Oxidation States
- +3
- Abundance in Crust
- Vanishingly rare
- Discovered
- 1952
- Discovered By
- Lawrence Berkeley National Laboratory
Electron Configuration
[Rn] 5f12 7s2
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f12
Ionisation Energies (kJ/mol)
- 1. 627
Elements near Fermium
Elements in the same group share the number of outer electrons and behave in similar ways. Elements in the same period share a shell, so they change steadily from left to right.